Models of Forbidden Line Emission Profiles from Axisymmetric Stellar Winds

Richard Ignace and Adam Brimeyer

East Tennessee State University

A number of strong infrared forbidden lines have been observed in several
evolved Wolf-Rayet star winds, and these are important for deriving
metal abundances and testing stellar evolution models. In addition,
because these optically thin lines form at large radius in the wind,
their resolved profiles carry an imprint of the asymptotic structure of
the wind flow. This work presents model forbidden line profile shapes
formed in axisymmetric winds. It is well-known that an optically thin
emission line formed in a spherical wind expanding at constant velocity
yields a flat-topped emission profile shape. Simulated forbidden
lines are produced for a model stellar wind with an axisymmetric density
distribution that treats the latitudinal ionization self-consistently and
examines the influence of the ion stage on the profile shape. The
resulting line profiles are symmetric about line centre. Within a
given atomic species, profile shapes can vary between centrally peaked,
doubly peaked, and approximately flat-topped in appearance depending on
the ion stage (relative to the dominant ion) and viewing inclination.
Although application to Wolf-Rayet star winds is emphasized, the concepts
are also relevant to other classes of hot stars such as luminous blue
variables and Be/B[e] stars.

Reference: To appear in MNRAS
Status: Manuscript has been accepted